I am analyzing a signalized intersection with right turn slip lanes that by-pass the signal, but are controlled by yield signs at the intersection roadway. The right turn volume is high and the conflicting through movement is also high. The Synchro queuing report states that the right turn queue length is zero. I suspect that Synchro sees that the right turn movement is not controlled by the signal and, therefore, automatically reports a zero queue length. However, that probably does not accurately reflect the actual field conditions. With a high volume of right turns and a high conflicting movement, there will be a queue, especially when the conflicting thru movenent has a substantial g/c ratio.

First of all, I would like to confirm that Synchro does not attempt to calculate the queue for the free right turn with a yield at a siganlzied intersection. Second, if that is the case, how can I use Synchro to calculate the right turn queue and possibly the LOS for that right turn movement at the intersection.

Thanks,

T Brown

Hi,

Yes, Synchro will handle a Free right as 100% green time. In that sense, the delays and queues will be zero (until you reach saturation). The channelized right options are really for simulation purposes.

To calculate a queue, set some timing in the TIMING window for the movement. For instance, a yield could be modeled as a pm+ov with RTOR set to yes.

Thanks,

John.

I have a similar issue I haven't figured out related to a diverge point/ off-ramp. Per the Synchro Manual recommendations, I modeled the exit ramp as 3-legged, unsignalized intersection with free movements. Looking at two different configurations: (T, TR, R) and (T, T, TR). Trying to determine any queuing in either the through movements or the right exit movements.

The queueing and blocking report isn't consistent, and I don't know why. I'm running the reports just for the unsignalized diverging intersections.

Some runs will show all the lanes and their respective queues. Some runs will show some of the lanes, but not all of them. Some runs are totally blank and don't show any movements or queues.

Does anyone know what I'm encountering here, and the best way to correctly model the queuing?

T Brown
If the right does not have its own accel lane you can not call it free-flow. it is yield, whether there is an yield sign or not. in the right turn channelized, put yield with Zero lane ad. make sure turn type is perm. it should give you delay and/or queue.

indivisibleoptimusprime
if it is a ramp. you should not use synchro. you may use simtraffic. you need to make modifications for that. i do not think i understand your problem. how come you have diufferent runs for synchro. please clarify.